Ferenc Hartung Tamás Insperger Gábor Stépán Janos Turi Approximate stability charts for milling processes using semi-discretization. 51-73 2006 174 Applied Mathematics and Computation 1 http://dx.doi.org/10.1016/j.amc.2005.05.008 db/journals/amc/amc174.html#HartungIST06